U.S. patent number 4,785,760 [Application Number 07/136,844] was granted by the patent office on 1988-11-22 for sprayer installation.
This patent grant is currently assigned to S A M E S S.A.. Invention is credited to Roger Tholome.
United States Patent |
4,785,760 |
Tholome |
November 22, 1988 |
Sprayer installation
Abstract
A sprayer installation suitable for spraying water-based paint
includes a multi-axis robot carrying a sprayer. A conveyor carries
objects to be sprayed past the robot. Respective circuits for
distributing products to be sprayed comprise first connection
devices at fixed locations within range of the robot. The robot
carries a storage tank for the product to be sprayed at least
during a spraying phase. This storage tank is connected to the
sprayer to supply product to be sprayed to it. First complementary
connection devices fitted to or communicating with the storage tank
cooperate with the first connection devices of any selected
distribution circuit.
Inventors: |
Tholome; Roger (La Tronche,
FR) |
Assignee: |
S A M E S S.A. (Meylan,
FR)
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Family
ID: |
9346679 |
Appl.
No.: |
07/136,844 |
Filed: |
December 22, 1987 |
Foreign Application Priority Data
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Jan 2, 1987 [FR] |
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87 00007 |
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Current U.S.
Class: |
118/323; 118/302;
118/668; 239/587.2; 901/43; 118/326; 239/305; 239/588 |
Current CPC
Class: |
B05B
13/0452 (20130101); B05B 5/1675 (20130101); B05B
5/1625 (20130101); B05B 5/1633 (20130101); B05B
12/14 (20130101); B05B 7/1404 (20130101) |
Current International
Class: |
B05B
13/02 (20060101); B05B 13/04 (20060101); B05B
5/00 (20060101); B05B 5/16 (20060101); B05B
001/28 () |
Field of
Search: |
;118/323,300,305,663,302,697 ;901/43 ;239/112,124,305,750,587 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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773048 |
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Dec 1967 |
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CA |
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EP192338 |
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Aug 1986 |
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EP |
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2149323 |
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Jun 1985 |
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GB |
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2166982 |
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May 1986 |
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GB |
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Primary Examiner: Beck; Shrive
Assistant Examiner: Dang; Vi Duong
Attorney, Agent or Firm: Sandler & Greenblum
Claims
I claim:
1. Sprayer installation comprising at least one multi-axis robot, a
sprayer carried by said robot, a conveyor adapted to carry objects
to be sprayed past said robot, respective circuits for distributing
products to be sprayed, like first connection means for each of
said distribution circuits at fixed locations within range of said
robot, a storage tank for product to be sprayed carried by said
robot at least during a spraying phase and connected to said
sprayer to supply thereto product to be sprayed, and first
complementary connection means equipping or communicating with said
storage tank and cooperable with said first connection means of any
of said distribution circuits.
2. Installation according to claim 1, comprising a single storage
tank fixed to said robot at a position near said sprayer.
3. Installation according to claim 2, comprising a cleaning product
distribution circuit and means situated in range of said robot for
connecting said cleaning product distribution circuit to said
storage tank.
4. Installation according to claim 2, comprising a waste evacuation
circuit and means situated in range of said robot for connecting
said waste evacuation circuit to said storage tank.
5. Installation according to claim 2, comprising a waste recovery
receptacle situated in range of said robot and adapted to receive
product rejected by said robot.
6. Installation according to claim 1, wherein the number of said
storage tanks is at least as large as the number of said
distribution circuits, said robot comprises second connection
means, second complementary connection means are provided on each
storage tank and said second connection means on said robot are
cooperable with said second complementary connection means on each
storage tank.
7. Installation according to claim 6, wherein each distribution
circuit is of the kind in which the product circulates continuously
in use and comprises a flow restrictor device, said first
connection means comprise two first connector parts spaced by a
predetermined distance and disposed one on each side of said flow
restrictor device and said first complementary connection means
comprise two first complementary connector parts spaced by said
predetermined distance lengthwise of said storage tank.
8. Installation according to claim 7, wherein said two first
connector parts are disposed at different levels with that at the
higher level downstream of that at the lower level relative to the
direction in which the product circulates in said circuit.
9. Installation according to claim 7, further comprising a
three-way valve in each distribution circuit and a discharge
circuit to which an outlet of each three-way valve is connected and
wherein said first connector part downstream of the other first
connector part relative to the direction in which the product
circulates in said circuit is connected to said circuit by said
three-way valve.
10. Installation according to claim 9, comprising a single
discharge circuit common to all said three-way valves.
11. Installation according to claim 1, comprising at least two
storage tanks, two storage tank receptacles, first connection means
on each receptacle, first complementary connection means on each
storage tank cooperable with said first connection means, second
connection means on said robot, second complementary connection
means on each storage tank cooperable with said second connection
means, a set of valves, cleaning product distribution circuit, a
waste evacuation circuit, a compressed air supply circuit and a
distributor-manifold connected by said set of valves to said
distribution circuits for product to be sprayed, to said cleaning
product distribution circuit, to said waste evacuation circuit, to
said compressed air supply circuit and to said two storage tank
receptacles.
12. Installation according to claim 11, wherein said first
connection means of each receptacle comprise two connector parts
spaced by a predetermined distance respectively connected by valves
of said set of valves to an outlet of said distributor-manifold, to
said waste evacuation circuit and to said compressed air supply
circuit and wherein said first complementary connection means of
each storage tank comprise two connector parts spaced by said
predetermined distance.
13. Installation according to claim 12, wherein said
distributor-manifold comprises respective inlets connected by
valves of said set of valves to said distribution circuits for
products to be sprayed, to said cleaning product distribution
circuit ana to said compressed air supply circuit and an outlet
connected by a valve of said set of valves to said waste evacuation
circuit.
14. Installation according to claim 1, comprising respective guides
disposed around each of said first connection means.
15. Installation according to claim 12, wherein said connector part
of said first connection means connected to said outlet of said
distributor-manifold is disposed at a lower level than the other
connector part of said first connection means connected to said
waste evacuation circuit and to said compressed air supply
circuit.
16. Installation according to claim 6, further comprising a
compressed air supply circuit and respective connector parts on
said robot connected to said compressed air supply circuit and said
sprayer, and wherein said second complementary connection means on
each storage tank comprise two connector parts spaced by a
predetermined distance one of which is cooperable with said
connector part on said robot connected to said compressed air
supply circuit and the other of which is cooperable with said
connector part on said robot connected to said sprayer.
17. Installation according to claim 11, further comprising a
compressed air supply circuit and respective connector parts on
said robot connected to said compressed air supply circuit and said
sprayer, and wherein said second complementary connection means on
each storage tank comprise two connector parts spaced by a
predetermined distance one of which is cooperable with said
connector part on said robot connected to said compressed air
supply circuit and the other of which is cooperable with said
connector part on said robot connected to said sprayer.
18. Installation according to claim 6, further comprising a
compressed air supply circuit and a connector part on said robot
connected to said compressed air supply circuit and wherein said
second complementary connection means on each storage tank comprise
a connector part cooperable with said connector part on said robot
connected to said compressed air supply circuit and said storage
tank carries a dedicated sprayer.
19. Installation according to claim 11, further comprising a
compressed air supply circuit and a connector part on said robot
connected to said compressed air supply circuit and wherein said
second ccmplementary onnection means of each -sorage tank comprise
a connector part cooperable with said connector part on said robot
connected to said compressed air supply circuit and said storage
tank carries a dedicated sprayer.
20. Installation according to claim 1, comprising a high-tension
voltage source connected to said robot and means for disabling said
high-tension voltage source when said sprayer is inoperative.
21. Installation according to claim 20, wherein said distribution
circuits for product to be sprayed are adapted to contain different
color water-based paint.
22. Installation according to claim 1, wherein each storage tank
comprises divider means dividing it into two chambers of which one
is adapted to contain a product to be sprayed and the other is
adapted to be connected to a compressed air supply circuit.
23. Installation according to claim 22, wherein said divider means
comprise a piston.
24. Installation according to claim 22, wherein said divider means
comprise a deformable membrane.
Description
BACKGROUND OF THE INVENTION
1. Field of the invention
The invention relates to an installation for spraying coating
products such as paint of the type in which the object to be
coated, carried by a conveyor, passes in front of the working area
of a manipulator robot carrying a sprayer which sprays the coating
product in the form of fine particles.
The invention is more particularly directed to a new arrangement
making it possible to solve the problem of changing color when the
objects passing in succession in front of the robot have to be
painted different colors and the problem of providing the necessary
galvanic isolation between the means for distributing the coating
products and the sprayer means where the paint used has a low
resitivity (water-based paint) and when the spraying means
incorporate a high-tension voltage source for implementing
electrostatic spraying.
2. Description of the prior art
A paint spraying installation in a production unit as large as an
automobile factory, for example, generally comprises several closed
loop paint distribution circuits which are very long (these
circuits may pass right across part of the plant) and which make
the connections between large paint storage tanks and the various
spraying booths. It is therefore necessary to provide a circuit of
this kind for each color and another circuit of the same kind for
the solvent or cleaning product. For obvious safety reasons these
circuits are electrically grounded.
In a spray booth supplied in this way, the objects to be painted
(which are automobile bodies in the example under discussion) are
carried by conveyor means through the booth in which is at least
one robot carrying a paint sprayer and able to operate within a
particular "working area" inside the booth. Use is routinely made
of robots having up to six or even seven degrees of freedom or axes
so that the sprayer can be oriented at will and caused to penetrate
into certain less accessible parts of the object to be painted. For
simple shapes a robot with only three of four degrees of freedom
may be adequate.
The sprayer may be of the electrostatic type involving high
rotation speeds, or of the pneumatic or hydrostatic type. The robot
usually comprises an arm made up of several segments articulated to
each other, the arm possibly being carried by a chassis movable
lengthwise of the conveyor means. One of the usual problems to be
overcome in this type of installation is that of changing color
between two consecutive objects. In the automobile industry in
particular there is no question of painting long series of bodies
the same color. To the contrary, the more usual situation is that
where the color has to be changed after virtually every body. This
implies the possibility of implementing extremely rapid rinsing and
drying cycles for the spraying means. To give an example, it may be
necessary to change the color about once a minute and all the
operations necessary for changing color can take about ten
seconds.
In conventional installations as currently known all the coating
product distribution circuits, a compressed air supply circuit and
a cleaning product circuit are connected through selectively
operable isolating valves to a manifold which has a common outlet
branch connected to the sprayer.
To change color it is necessary to shut off the valve in the
circuit for the coating product currently being used a particular
(computed) time before the end of the current spraying phase and
then to open the compressed air valve to expel the remaining
product through the sprayer. The robot is then moved away from the
object and oriented towards a recovery receptacle. The cleaning
product valve is opened until the manifold and the sprayer are
clean. This valve is then closed and the compressed air valve is
opened again to expell the cleaning product contained in the
manifold into the recovery receptacle. The opening of the
compressed air valve is prolonged to dry the conduits and then,
once it has been closed, the valve on another coating product
circuit is opened to fill the manifold and the conduits until a
little of the new color coating product is expelled from the
sprayer. The robot is then turned back to face the new object to be
sprayed.
If the installation comprises only a small number of different
color coating products, three or four, for example, the manifold
may be disposed relatively near the sprayer, on one of the final
articulated segments of the robot arm, for example, each coating
product being supplied through a flexible hose. On the other hand,
if there are too many different coating products (there may be up
to 20) this solution is no longer practicable and the manifold must
then be fixed with its outlet connected to the sprayer by a single
flexible hose. If the objects to be sprayed are bulky, which is the
case with automobile bodies, the robots have to move over great
distances parallel to the largest dimension of the objects to be
sprayed, which may be five or six meters, for example. In this case
the manifold is far away from the sprayer, up to ten meters, for
example, which considerably increases the volumes of conduit to be
cleaned and therefore the length of the color change sequences. It
often becomes necessary in such cases to duplicate the supply
circuits (manifolds, valves, conduits) in order to use part for
spraying while the other part is undergoing a cleaning and color
change cycle. Also, the quantities of the coating product and of
the cleaning product wasted on each color change are important, in
the order of several hundred cubic centimeters.
Furthermore, the installation is made more complex by the fact
that, in order to procure a constant flowrate of the coating
product during the end of the spraying phase in which the coating
product is expelled by compressed air, it is necessary to provide a
pressure regulator immediately upstream of the sprayer on the
coating product circuit. Finally, as the sprayers generally have
very small cross-section outlet orifices, to secure correct
spraying, it is not always possible to eject all of the cleaning
product through these orifices. For the cleaning of the manifold
and the conduits to be effective and fast it is necessary to
maintain turbulent flow and therefore a high speed combined with a
high flowrate. To this end it is necessary to provide between the
pressure regulator and the sprayer a large cross-section purging
circuit and a purging valve through which the cleaning product
flows to the recovery receptacle. Also, the pressure regulator and
the purge valve being in the immediate vicinity of the sprayer, in
an area that may contain a flammable gaseous mixture and that may
be at a high-tension voltage when the sprayer is of the
electrostatic type, this device is usually actuated by compressed
air, calling for additional pneumatic hoses.
In the case of an electrostatic installation all these problems
concerning color changes are accentuated where there is a
requirement to use coating products of low resistivity, such as
water-based paint, for example, while conserving the advantages of
electrostatic spraying. In this case the sprayer is often held at a
high-tension voltage and it is necessary to avoid short-circuits
between the sprayer and the coating product distribution circuits
that are electrically grounded. For the leakage current to be
acceptable with the water-based paints currently used it would be
necessary to use insulative conduits with a length/cross-section
ratio that would be unacceptable because it would lead to extremely
long color changing times and unrealistically large quantities of
coating and cleaning product being wasted.
Also, when the coating product supply conduits and the purge
circuits are filled with electrically conductive product,. the
dielectric strength of the conduits must be sufficiently high to
withstand the high-tension voltage applied. Also, the quantity of
product that they contain represents a relatively large electrical
capacity able to store a quantity of energy much higher than the
tolerated limits.
To confront the problem specific to changing color with
low-resistivity coating products, French Patent No. 2 572 662
proposes to fill an intermediate storage tank with just the
quantity of paint needed for each application. This intermediate
storage tank is fixed so that each color change entails cleaning
out not only the storage tank but also all the conduits connected
to it. Furthermore, in one embodiment isolation is re-established
after filling by draining and drying a sufficient length of conduit
upstream of the intermediate storage tank. This operation requires
a prohibitive length of time on each color change.
The invention proposes to solve the problems of changing color by
considerably simplifying the equipment situated between the
distribution circuits and the sprayer, irrespective of the type of
coating product used.
The invention also proposes to reduce the time necessary to change
color, even when the number of different colors is large and the
robot which moves the sprayer has to move over long distances
because of the size of the objects to be sprayed.
In the specific instance of electrostatic spraying of
low-resistivity coating products, the invention further proposes to
solve in a particularly simple way the problem of isolating the
electrostatic sprayer from the coating product distribution
circuits, that are electrically grounded.
SUMMARY OF THE INVENTION
The present invention consists in a sprayer installation comprising
at least one multi-axis robot, a sprayer carried by the robot, a
conveyor adapted to carry objects to be sprayed past the robot,
respective circuits for distributing products to be sprayed, like
first connection means for each of said distribution circuits at
fixed locations within range of the robot, a storage tank for
product to be sprayed carried by the robot at least during a
spraying phase and connected to the sprayer to supply thereto
product to be sprayed, and first complementary connection means
equipping or communicating with the storage tank and cooperable
with the first connection means of any of the distribution
circuits.
There are multiple embodiments corresponding to this definition.
Thus the coating product storage tank may be fixed to the end of
the robot arm. In this case it is sufficient for this arm to be
able to orient itself on each color change towards the
aforementioned connection means as well as towards other connection
means of a cleaning product distribution circuit in order to clean
the storage tank and then fill it with a coating product of a
different color. It is equally possible to use as many storage
tanks as there are different coating products. In this case, each
storage tank may be separated from the robot arm and "hooked onto"
its own distribution circuit to be refilled after use. This
embodiment dispenses with the need for cleaning the storage tanks.
Finally, an intermediate solution might consist in using only two
removable storage tanks, one of the storage tanks being carried by
the robot arm while the other is connected to the coating product
and cleaning product distribution circuits to undergo a color
change cycle.
In all cases, note that the quantity of coating product fed into
the storage tank for each spraying phase has no need to be adjusted
according to the dimensions of the object to be painted. The
dimensions of the storage tank depend only on the ability of the
robot to support and move at high speed a particular weight of
coating product. If the robot is unable to support a storage tank
of sufficiently large dimensions to contain all of the coating
product needed for painting the entire object, it is perfectly
feasible to envisage recharging this storage tank one or more times
during the dead time of the spraying phase. If, on the other hand,
the capacity of the storage tank can accommodate more coating
product than is necessary for a spraying phase the excess quantity
is re-injected into the corresponding distribution circuit at the
beginning of the color change cycle.
The invention will be better understood and other advantages of the
invention will emerge more clearly from the following description
of several paint spraying installations in accordance with the
invention given by way of example only and with reference to the
appended diagramatic drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a sprayer installation during a paint
spraying cycle, using a robot with several degrees of freedom and
incorporating improvements in accordance with the invention.
FIG. 2 is a schematic view analogous to figure 1 showing the
position of the robot during a color change cycle.
FIG. 3 is a plan view of FIG. 2.
FIG. 4 is a schematic showing one embodiment of the invention.
FIG. 5 is a plan view of FIG. 4.
FIG. 6 is a schematic view showing another embodiment of the
invention.
FIG. 7 is a plan view of FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 through 3, a first embodiment of the invention
comprises a paint spray booth 11 through which pass conveyor means
12 carrying objects 13 to be painted (automobile bodies in this
case) past a robot 14 in close proximity thereto. This robot is of
the multi-axis type, known in itself; it essentially comprises a
chassis 15 movable along a guide 16 extending over a certain
distance alongside the conveyor means and an arm 18 carried by the
chassis and made up of several segments 18a, 18b, 18c articulated
to each other. The chassis 15 itself comprises two parts 15a, 15b
joined together by a vertical axis articulation enabling it to
pivot on itself as seen are comparing FIGS. 1 and 2. The "working
area" of the robot is anywhere in the booth that the robot can
reach, in particular by means of the last segment 18c of its
arm.
The segment 18c carries the coating product spraying means, in this
instance a sprayer 20 supplied with compressed air by a flexible
hose 21 and, in accordance with the invention, a coating product
storage tank 22. In the case of an electrostatic sprayer
installation, the robot may comprise a high-tension voltage
generator 24 connected to the spray nozzle or to the bowl in the
case of a sprayer of the type relying on a high rotation speed. In
a conventional way the high-tension voltage generator 24 is fully
controllable, by which is meant that its output voltage may be
reduced to zero volts at any time and then re-established virtually
instanteously, using highly conventional control means. This
possibility of adjusting the high-tension voltage, although banal
in itself, is of particular importance in the context of the
invention since for each filling and/or cleaning sequence the
sprayer is coupled up to the product distribution circuit, which is
electrically grounded.
In the example now being described, the storage tank 22 is fixed
onto the last segment of the robot and communicates with the
sprayer 20. If the storage tank is too large to be mounted on the
last segment, it can be mounted on the penultimate segment and
connected to the sprayer by a flexible hose.
Conduits forming part of the various distribution circuits pass
through the booth 11; they may be fixed along the length of a wall
26 of the latter, for example. Thus in the example shown there are
three paint distribution circuits P1, P2 and P3 (these are for
paints of different colors), a cleaning product distribution
circuit N and a waste evacuation circuit D. There is also a
compressed air supply circuit A to which the conduit 21 is
connected via a valve 25. The circuits P1, P2 and P3 are provided
with respective first connection means 28a which are similar (like
to each other), and grouped together in the working area of the
robot, that is the vicinity of the wall 26. Each of these first
connection means of any of the circuits P1, P2, P3 is cooperable
with first complementary connection means 29a carried by the
storage tank 22. In the case of FIGS. 1 through 3, said first
connection means of each circuit P1, P2 and P3 are simply and
respectively constituted by a single connector part of the
"ball-type self-closing quick-release connector" type well known to
those skilled in the art whereas the first complementary connection
means 29a consist only of another connector part of complementary
structure adapted to connect in a fluid-tight way to one of the
connector parts of circuit P1, P2 or P3. Likewise, the cleaning
product distribution circuit N and the waste evacuation circuit D
respectively comprise connection means 28b, 28c to the storage tank
22, in this instance identical to said first connection means of
the circuits P1, P2 and P3 since they are made up from the same
connector parts. All the connection means 28a, 28b, 28c are grouped
very close to each other in the working area of the robot.
A waste recovery receptacle 30 is also provided in the working
area, not far from the connection means 28a, 28b and 28c. This
receptacle is designed to receive any product (paint or cleaning
product) expelled in jet form by the sprayer 20.
Note that the compressed air hose 21 may communicate direct with
the storage tank 22 if the robot is programmed so that it never
places the pressurization air inlet at a level lower than the paint
outlet, to prevent air being expelled directly by the sprayer, when
it is opposite an object to be painted. A known system for
monitoring the quantity of paint sprayed makes it possible to avoid
complete emptying of the storage tank during spraying. Use may also
be made of another type storage tank comprising a piston or a
deformable membrane adapted to divide the internal space of the
storage tank into two chambers. One chamber receives the product
and the other is filled with air under pressure. In this case it is
obvious that the first complementary connection means 29a
communicate with the chamber receiving the product and the conduit
21 communicates with the other chamber so as to push back the
piston or the membrane as the product is taken off by the sprayer
20 or by the first complementary connection means 29a.
The operation of the installation will now be described. At the end
of a spraying phase shown in FIG. 1 when the valve 25 is open to
enable compressed air to propel the coating product to the sprayer
20 where it is sprayed towards the object to be painted the robot
15 turns on its axis to bring the storage tank 22 into the area of
the booth containing the various connection means described
hereinabove. If it is necessary to change the color of the paint,
for example to change from the paint distributed via P1 to the
paint distributed via P2, the robot begins by connecting the
storage tank to circuit P1 in order to re-inject into it the excess
paint or at least as much as possible of this excess, monitoring
the quantity expelled to prevent injecting air into the circuit.
The robot then places the storage tank 22 in communication with the
circuit 21 distributing the cleaning product N, the three-way valve
25 being vented to the atmosphere to enable filling of the storage
tank. When the storage tank is filled the robot connects it, via
the same connection means, to the waste evacuation circuit D and
the valve 25 is again connected to evacuate the cleaning product in
this circuit. The previous two operations are repeated as many
times as necessary until the storage tank is clean. After this the
robot moves the sprayer 20 to the receptacle 30 and compressed air
is again injected to expel a little of the cleaning product through
the sprayer in order to clean it. The robot then connects the
storage tank 22 to the distribution circuit P2 while circuit 21 is
again vented to atmosphere by the valve 25 to enable the storage
tank to be filled with new paint. After this the robot moves the
sprayer 20 over to the receptacle 30 in order to spray into it a
small quantity of the product and thus eliminate the last traces of
the cleaning product. The color change cycle is then finished and
the robot can again turn on its axis to paint a new body.
In the case of an electrostatic sprayer installation the
high-tension voltage is reduced to zero before the color change
cycle is started and is not re-established until it has finished.
It is clear that through the spraying time the high-tension voltage
is totally isolated from the various distribution circuits that are
electrically grounded since there is no product conduit between
them.
It will also be appreciated that the equipment carried by the robot
is highly simplified. The conventional purge valves and purge
circuit are eliminated since, on cleaning out the storage tank 22,
the products are fed in and evacuated essentially by the connection
means described hereinabove, which have a much larger cross-section
than the sprayer 20. The cleaning product is admitted into the
sprayer 20 only in very small quantities, for cleaning just the
sprayer. Likewise, no pressure regulator is needed since the
installation does not comprise any long pipes in which paint is
propelled by compressed air at the end of the spraying period. Here
the paint is propelled into the storage tank where there is no
variation in head loss.
FIGS. 4 and 5 where analogous parts carry the same reference
numbers show an embodiment in which the color change cycle can be
very significantly abbreviated, as it does not require any
cleaning. The installation is provided with as many coating product
storage tanks 22.sub.1, 22.sub.2, 22.sub.3, etc as there are
distribution circuits P.sub.1, P.sub.2, P.sub.3, etc. Thus these
storage tanks are not fixed onto the robot but are connected to it
by means of second connection means (not shown) carried by the
robot and cooperable with second complementary connection means
34a, 34b provided on each storage tank. These connection means are
made up from the same connector parts as those used in the first
embodiment described. However, the second connection means provided
on the robot comprise two connector parts spaced by a predetermined
distance while the second complementary connection means 34a, 34b
also comprise two corresponding connector parts spaced by the same
distance in order to fit to the parts carried by the robot. Once
the storage tank is in place on the robot one of the connector
parts of the storage tank is connected to the compressed air supply
while the other is connected to the sprayer. Each storage tank may
be of the piston or deformable membrane type described
hereinabove.
The aforementioned first connection means of each distribution
circuit P1, P2 or P3 also comprise two connector parts 28a.sub.1,
28a.sub.2. These are spaced by a predetermined distance with one on
each side of a restriction 35 connected in series into the
corresponding circuit P1, P2 or P3, this circuit being as usual of
the continuous circulation closed loop type.
Analogously, said first complementary connection means provided on
each storage tank comprise two other connector parts 29a.sub.1,
29a.sub.2 spaced by the same distance lengthwise of said storage
tank.
In an advantageous arrangement the height of the circuits P1, P2
and P3 varies to each side of the restriction 35. The arrangement
is such that the two connector parts 28a.sub.1, 28a.sub.2 are
disposed at different levels, the connector part 28a.sub.1 at the
higher level being downstream of the other connector part relative
to the direction in which the coating product circulates in the
corresponding distribution circuit. Also, the connector part
28a.sub.1 on the downstream side is connected to the distribution
circuit through the intermediary of a selectively operated
three-way valve 36 the other outlet of which communicates with a
discharge circuit 37. This latter circuit is common to all the
valves 36. The operation of this installation will now be
described.
When the robot has finished painting an object and it is necessary
to change color it "hooks up" the storage tank to said first
connection means 28a.sub.1, 28a.sub.2 of the distribution circuit
of the corresponding color. The robot then takes up the storage
tank connected to another circuit corresponding to the new color.
The robot is then immediately ready to paint the next object.
During this time the storage tank that has just been "hung up" is
gradually filled, the corresponding valve 36 being in communication
with the discharge circuit 37. Because a slight head loss is
created in the corresponding distribution circuit by the
restriction 35 the paint fills the storage tank until a small
quantity is evacuated from it via the discharge circuit 37. At this
time the storage tank is full and again ready for use. The valve 36
is then switched over and the paint continues to flow slowly
through the storage tank until the robot takes up that storage tank
again. The circulation of paint in the storage tank prevents the
various constituents of the paint settling out. The high-tension
voltage is reduced to zero throughout the hanging up phase of one
storage tank and the taking up phase of another storage tank, of
course. Two storage tanks may be provided for each color, so as to
further limit the dead time if two consecutive objects are to be
painted the same color or if a storage tank does not have
sufficient capacity for painting all of an object.
The embodiment of FIGS. 6 and 7 shows a solution mid-way between
the previous two, to the extent that it comprises only two storage
tanks (or at least one pair of such storage tanks) and rinsing and
drying means. The two storage tanks 22 are similar to those of the
embodiment of FIGS. 4 and 5. Thus they each comprise first
complementary connection means 29a.sub.1, 29a.sub.2 and second
complementary connection means 34a, 34b each comprising two
connector parts. The robot is provided with second connection means
similar to those of the embodiment of FIGS. 4 and 5. The two
storage tanks are designed to be "hooked onto" respective
receptacles each comprising the previously mentioned first
connection means 28a.sub.1, 28a.sub.2 cooperable with said first
complementary connection means provided on the storage tanks. These
first connection means also comprise two connector parts each.
As in FIG. 1, the installation comprises coating product
distribution circuits P1, P2, P3, a cleaning product distribution
circuit N, a waste evacuation circuit D and a compressed air supply
circuit A. The storage tanks are supplied sequentially and
selectively through the intermediary of a distributor-manifold 40
comprising two outlets 41a, 41b connected by selectively operated
valves 42 to the first connection means and a certain number of
inlets, including three inlets 43.sub.1, 43.sub.2, 43.sub.3
connected by selectively operated valves 44 to circuits P1, P2, P3.
It further comprises an inlet 45 connected by a selectively
operated valve 46 to the cleaning product distribution circuit N
and an inlet 47 connected by a selectively operated valve 48 to the
compressed air supply circuit A.
For each of the two storage tank receptacles, one (28a.sub.2) of
the two connector parts of the first connection means is connected
to an outlet 41a or 41b of the distributor-manifold and the other
(28a.sub.1) is connected to the waste evacuation circuit D by a
selectively operated valve 50 and to the compressed air supply
circuit A by a selectively operated valve 52. The
distributor-manifold 40 further comprises another outlet 54
connected by a selectively operated valve 56 to the waste
evacuation circuit D. For each storage tank receptacle, the
connector part (28a.sub.2) of said first connection means which is
connected to the outlet of the distributor-manifold is at a lower
level than the other connector part (28a.sub.1) connected to the
waste evacuation circuit D and to the compressed air supply circuit
A.
Each storage tank receptacle can be provided with guides 60 to
facilitate the approach and correct positioning of the storage tank
in the case where the robot does not provide the necessary accuracy
of positioning. Such guides may be provided in the vicinity of the
storage tank supports or equally well on the robot itself. Such
guides may of course be used in installations as shown in FIGS. 1
through 5. The operation of the embodiment shown in FIGS. 6 and 7
will now be described.
When the robot has finished painting an object it "hangs up" one of
the storage tanks 22 at one of the two locations provided for this
purpose. It can then take up the second storage tank before turning
back to paint the next object. During this time the
distributor-manifold 40 carries out a cleaning and refilling cycle
on the previous storage tank. To this end the excess paint in this
storage tank is first re-injected into the circuit P1, P2 or P3 for
the corresponding color by opening the corresponding valves 52, 42
and a valve 44. The storage tank is then cleaned by injecting the
cleaning product through the valve 46, the distributor-manifold and
the same valve 42, the corresponding valve 50 being open and the
corresponding valve 52 being closed. After a phase in which the
storage tank is dried by circulating air, by closing the valve 46
and opening the valve 48, it is placed in communication with the
circuit of the new paint, through the intermediary of one of the
valves 44 and the distributor 40, until a small quantity of excess
paint is evacuated into the circuit D. After the valves 42, 44, 50
are closed the storage tank is ready to be used again. The cycle
ends with the cleaning and drying of the distributor-manifold
itself.
Although the embodiments of the invention have been described in
the case of spraying (electrostatic or otherwise) liquid product
such as paint, it goes without saying that it is equally applicable
to powdered products such as powder paint, for example. It then
suffices for the mobile intermediate storage tank or tanks and the
transport, spraying, cleaning, recovery, etc means to be adapted in
ways well known to those skilled in the powder spraying art to suit
the relevant powder products. For example, it suffices to
substitute for pressurization of the storage tank fluidization of
the powder by feeding air through a porous bottom, to substitute
for cleaning by means of solvent blowing out with compressed air,
to substitute for self-closing ball-type connectors known elastic
sleeve valves, to substitute for the waste receptacle a suction
hood fitted with a separator filter, etc.
The foregoing description has made virtually exclusive reference to
changing the coating color, but it is obvious that these changes
can also relate to the nature of the product constituting the
coating.
It is to be understood that the invention is in no way limited to
the embodiments described hereinabove. In particular, if the
structure of the paint sprayer is relatively simple (air sprayer)
it (or part of it) may be combined with the storage tank. In this
case the complementary second connection means of each storage tank
comprise a connector part cooperable with a connector part of the
robot communicating with a compressed air supply while the storage
tank itself carries a dedicated sprayer communicating with the
interior of the storage tank.
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